Regex testing

Test programs to compare performance of Rust and Java regexes without caching information between between matches. Accomplishes this by creating a new matcher for every match in Java and cloning a new Regex for every match in Rust.

The program reads a text file into memory and runs through the file 20 times with a regex that checks whether each line only contains certain characters. It only starts measuring time after the first pass to give Java's Hotspot a chance to optimize the code and better simulate a long-running application.

How to run

• Make sure Java and Rust are installed
• Download a large text file, for instance http://norvig.com/big.txt
• Compile Java, inside regexperf_java javac -d ./bin src/Regexperf.java
• Run Java, inside regexperf_java java -cp ./bin Regexperf ~/Downloads/big.txt
• Compile Rust, inside regexperf_rs cargo build --release
• Run Rust, inside regexperf_rs ./target/release/regexperf_rs ~/Downloads/big.txt

Results on OSX (2-core Macbook Pro)

Java 864340 out of 2569140 lines matched, timing 1636 ms (670 ns per match)
Rust 864340 out of 2569140 lines matched, timing 11677 ms (4784 ns per match)

Later added capability to specify batch sizes to the Rest test
Rust with batch sizes specified
864340 out of 2569140 lines matched, with batch size 10, timing 5498 ms (2252 ns per match)
864340 out of 2569140 lines matched, with batch size 100, timing 4073 ms (1668 ns per match)

Results on Windows 10 (Dell XPS 15 9550)

Java 864340 out of 2569140 lines matched, timing 1472 ms (603 ns per match)
Rust 864340 out of 2569140 lines matched, timing 13585 ms (5566 ns per match)